It is known that hearing aid devices that are configured to provide bony seal provide an adequate sealing of the ear canal, and that this seal can preclude undesirable acoustic feedback. Several types of hearing aid devices are adapted to be fitted partly in a fleshy (cartilaginous) region and partly in a bony region of the ear canal in order to form a seal for the ear canal in the bony region of the ear canal.
Completely-in-the-canal (CIC) hearing aid devices and receiver-in-the-ear (RITE) hearing aid devices may be adapted for insertion into the bony region of the ear canal and hence these types of hearing aid devices may be capable of providing bony seal.
Even though bony seal is capable of reducing the quantity of undesirable acoustic feedback there is still need for further reduction of the acoustic feedback, especially in small hearing aid devices, in which the receiver and the microphone are arrange close to each other.
Bony seal hearing aid devices are either providing a complete or non-complete seal of the ear canal. When a complete seal is provided no ventilation occurs, however, when a non-complete seal is provided a vent is created in order to establish static pressure equalization between the small chamber between the hearing aid device and the ear drum and the surrounding atmosphere. In these types of bony seal hearing aid devices relative long time delays are acceptable without compromising on quality. In practice delay periods up to 10-20 ms could be used if the user should still be able to lip-read.
It is known to use frequency shift techniques in order to carry out electronic feedback reduction. It is also known that the frequency shift and the time delay of the processed sound signal are correlated and that the best electronic feedback reduction is associated with long time delays.
U.S. Pat. No. 6,097,823 A discloses a digital hearing aid that comprises a microphone, a control and modeling circuitry, and a receiver. The microphone receives an input sound signal and generates a digital input signal in response. The control and modeling circuitry filters and amplifies the digital input signal and performs feedback neutralization and feedback path modeling to generate a digital output signal. Hereafter the receiver receives the digital output signal and generates an output sound signal. This anti-feedback method applies time delay.
US2008205679 describes an in-ear auditory device having a receiver sized to fit within an ear canal of a user, a transducer and an isolator disposed to substantially acoustically isolate the transducer from the receiver. The auditory device is able to completely occlude the ear canal and having means for electronic feedback suppression.
US2002122563 describes a hearing aid for deep insertion where feedback is eliminated by electronically suppressing frequencies prone to generating feedback.
It is an object for the present disclosure to provide a method for electronic feedback reduction in a bony seal hearing aid device and to provide a bony seal hearing aid device having an improved electronic feedback reduction function.
Moreover, when the users own voice is active, the sound will travel by two paths: a) from the mouth to the air and into the hearing aid device and b) from bone/tissue conduction from the vocal organs to the hearing organs. Accordingly, interference between these two different signals gives rise to undesired sound quality issues.
Therefore, it is an object for the present disclosure to provide a “bony seal” hearing aid device, in which a high sound quality can be provided both when the voice of the user is active and inactive.